personal space

so i'm having lunch with a friend today at cafe express, and as i'm sure you know, they have counter service. it was around noon, and it was pretty crowded, and my friend and i were waiting in line. at first my friend was a little in front of me, and there was a woman behind me. i realized very quickly that she was EXTREMELY close to me, but i tried to ignore it. then she started turning her body every so often (i have no idea why), and every time she'd turn, she'd knock me in the back with her elbow. a normal person would realize, "hey, i keep hitting this girl. maybe i should back up a little." this lady, however, was not normal. i tried to back up a few inches to show her how close she really was, but that didn't work. then i tried to scoot up a few inches; she'd scoot up as well. who is this woman?? she was literally about 2 inches behind my back. then my friend and i switched lines b/c they opened a new register...and what do you know: close-stander was right behind us. when we switched lines, i stood in front of my friend, so close-stander was behind her now. same thing happening. after she had been knocked twice, my friend turned around to look at close-stander, and she replied with a smile, "oh, i'm sorry." but did she back up? NO. apparently there are people in this world who just have no personal space boundaries. no one ever says to them, "back off! you're too close," and they just go on irritating others. i should have said something, but frankly i was so annoyed at that point that i would have just been mean. so i said nothing, gave my order, and walked away, leaving her to annoy still more people.